The present invention relates to local oscillator circuits and, more particularly, to local oscillator circuits suitable for processing frequencies of the order of about 400-700 MHz.
The oscillation energy of a local oscillator circuit is often received by a pickup coil inductively coupled to an inner conductor of the oscillator circuit, and then amplified by an amplifier in the subsequent stage. However, the output level of the pickup coil may be lowered as the oscillation frequency grows higher. Such a phenomenon typically depends on the frequency characteristic of the active element, which typically is a transistor, of the local oscillator circuit. When such lowered oscillation signals are introduced in a subsequent stage, such as a mixer in a tuner for example, the frequency-conversion gain of the mixer will not be steady.